Infectious Diseases - Alamance-Burlington School System · PDF file Infectious Disease ......

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Transcript of Infectious Diseases - Alamance-Burlington School System · PDF file Infectious Disease ......

  • Infectious Diseases

  • • Pathogens: Microorganisms that are capable of causing disease

    • Infection: Results when a pathogen invades and begins growing within the host

    • Disease: Results only if and when normal tissue function is impaired

    • The body has defense mechanisms to prevent infection (i.e. burns, skin lesions)

  • • In order to cause disease, pathogens must be able to enter, adhere, invade, colonize, and inflict damage

    • Entrance to the host typically occurs through natural orifices such as the mouth, eyes, genital openings, or through wounds that breach the skin barrier to pathogens

    • Growth of pathogens or the production of toxins/enzymes cause disease

    • Some normal flora prevent diseases

  • Infectious Disease – a disease caused by the invasion of a host by pathogens causing impaired tissue function and can be transmitted to other individuals

    Five major types of infectious agents (microbes): bacteria, viruses, fungi, protozoa, and helminthes:

    • Bacteria: They contain no organized internal membranous structures. Most reproduce by growing and dividing into two cells in a process known as binary fission.

  • Types of Bacteria:

    • Salmonella typhi: a gram-negative organism that causes typhoid fever.

    • Yersinia pestis- Causes plague The reservoir is rodents. ***

    • Staphylococcus aureus- causes skin, respiratory and wound infections.

  • • Viruses: Infect all organisms from plants and animals to fungi and bacteria. They are not organisms themselves because apart from a host cell, they have no metabolism and cannot reproduce.***

  • Types of viruses:

    • Herpes viruses: cause chicken pox, cold sores, and painful genital lesions, and the pox virus that causes smallpox.

    • Rhinoviruses: cause most common colds.

  • Viruses (continued)

    • Myxoviruses and paramyxoviruses: cause influenza, measles, and mumps.

    • Rotaviruses: cause gastroenteritis. • Retroviruses: cause AIDS and several

    types of cancer.

  • Fungi: Reproduce primarily by forming spores.

    Types of diseases caused by fungi:

    • Ringworm • Histoplasmosis (a mild to severe lung

    infection transmitted by bat or bird droppings)

    • Candida genus: opportunistic pathogens*** that may cause diseases such as vaginal yeast infections and thrush.

  • Protozoa: Do not have cell walls and are capable of a variety of rapid and flexible movements.

    • Can be acquired by contaminated food or water or by the bite of an infected arthropod such as a mosquito.

  • Helminths: Simple, invertebrate animals, some of which are infectious parasites. Difficult to treat because the drugs that kill helminthes are frequently very toxic to human cells.

    Diseases caused by helminths:

    • Trichinella Spiralis: occurs when improperly cooked pork from infected pigs is ingested.

    – Symptoms include vomiting and diarrhea and fever***

    – Respiratory paralysis can occur in fatal cases of trichinella spiralis***

  • Prions: Infectious particles that consist of only protein.

    •Diseases caused by Prions: • Creutzfeldt-Jakob disease (in


    •Bovine spongiform encephalopathy (mad cow disease)

  • • Epidemiology- the study of the occurrence of disease in populations.

    •Disease reservoirs- The reservoir for a disease where the infectious agent survives (example: rodents, soil

    •Modes of transmission: Infectious agents may be transmitted through either direct or indirect contact.

  • Host defenses against infectious diseases:

    • Nonspecific mechanisms-the body’s primary defense against disease – these include anatomical barriers to invading pathogens, physiological deterrents to pathogens, and presence of normal flora. (skin, low pH and high salinity)

  • • Specific mechanisms of host resistance- our immune system

    • Immunity – when a host encounters an antigen that triggers a specific immune response for the second time and the body responds quickly and produces antibodies

    • Vaccination- produces immunity